On apatite fission-track analysis and heat transfer processes in the upper crust.

摘要

This dissertation consists of four independent chapters, each of which focuses on aspects of apatite fission-track analysis and/or processes that affect heat transfer in the upper crust.; Chapter 1 presents fission-track data from detrital apatites recovered from Ocean Drilling Program (ODP) Leg 116 cores of distal Bengal Fan sediments. Mean track lengths of samples from the upper 820 m of sediment penetrated at Site 717, and the upper 560 m of sediment penetrated at Site 718, range from 14.4 to 14.8 {dollar}mu{dollar}m and are diagnostic of rapidly cooled source areas. Mean track lengths from the lowermost 400 m of sediment penetrated at Site 718 decrease monotonically from 14.6 to 13.2 {dollar}mu{dollar}m and indicate bottom-hole paleo-temperatures of at least 50{dollar}spcirc{dollar}C. Dated samples have mean fission-track ages that are less than 10 m.y.-older than sample depositional ages, indicating source area rocks cooled at rates greater than 15{dollar}spcirc{dollar}C/m.y. since about 17 Ma.; Chapter 2 applies numerical models of time-dependent heat transfer to characterize the thermal history of sediments at the ODP sites. Results indicate that upward movement of pore fluids at velocities of 3 to 9 mm/yr are capable of explaining the fission-track data at Site 718 and elevated seafloor heat flow in this area. Available data suggests that anomalous thermal structure in the central Indian Ocean may represent a joint response to compaction-driven dewatering of the Bengal Fan and local enhancement of vertical permeability due to intraplate deformation.; Chapter 3 applies a stochastic inversion approach (simulated annealing) to quantify the thermal history information contained in synthetic apatite fission-track data. This approach allows determination of the range of thermal histories compatible with the data and indicates that temperature resolution is no better than {dollar}pm{dollar}10{dollar}spcirc{dollar}C.; Chapter 4 presents apatite fission-track data from surface and subsurface samples of Oligocene strata from the South Texas Coastal Plain. The data are used to evaluate apatite fission-track annealing models and should be amenable to analysis by inverse modeling to obtain better estimates of empirical parameters in these models.